Semiconductor package

ABSTRACT

A semiconductor package includes a base substrate on which semiconductor elements are disposed; a covering member which is provided to the base substrate, which covers the semiconductor elements, and which includes an opening at an end thereof at the side of the base substrate; and a connector substrate which is provided on the base substrate in a manner that the connector substrate closes the opening, which includes a first high-frequency signal line in an area located inside the covering member for a first surface, and which includes a second high-frequency signal line on a second surface being a surface on the opposite side of the first surface, the second high-frequency signal line being electrically connected to the first high-frequency signal line; wherein the base substrate is formed in a manner that the base substrate is located away from the second high-frequency signal line.

CROSS REFERENCE OF THE RELATED APPLICATION

This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2006-91162, filed on Mar. 29, 2006; the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor package, and particularly to a semiconductor package in which a semiconductor element is hermetically sealed.

2. Description of the Related Art

Semiconductor packages with semiconductor elements, such as high-frequency semiconductor elements, have been used for various high-frequency devices (for example, refer to JP-A 2001-35948(KOKAI)). Such semiconductor packages include one (a hermetic seal package) in which a semiconductor element is hermetically sealed, and which includes a base substrate to which the semiconductor element is disposed; a frame body which is provided on the base substrate, and which surrounds the semiconductor element; a lid body which is provided on the frame body; and a connector substrate which is passed through the frame body, and which is provided on the base substrate.

For example, as shown in FIG. 1, a connector substrate 101 is provided on a base substrate 102. The connector substrate 101 is formed of dielectrics, and is a substrate which closes an opening 104 formed in a frame 103 which is a frame body. The connector substrate 101 includes a convex part 105 for closing the opening 104, and a high-frequency signal line 106, which is passed through the convex part 105, is provided to a surface of the connector substrate 101. On the peripheral surface of the connector substrate 101, an outer frame 101 a to which W paste is applied, followed by sintering, is provided. The outer frame 101 a and the frame 103 are brazed with Ag, and a hermetic seal package is formed.

A portion, through which the high-frequency signal line 106 penetrates, functions as a triconductor part (a stripline part) 106 a, and other portion functions as a micro-strip line part. The triconductor part 106 a of the high-frequency signal line 106 is formed thinner than the micro-strip line part in order to match impedance of the triconductor part 106 a with that of the micro-strip line part (refer to FIG. 1).

However, recently, semiconductor packages have been developed into those with high power. When the width of the high-frequency signal line 106 is made smaller, the insertion loss of a high-frequency signal is increased, and allowable current of the high-frequency signal line 106 is lowered. Consequently, there are cases where the triconductor part 106 a of the high-frequency signal line 106 melts.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a semiconductor package with which melting of a high-frequency signal line due to high power can be suppressed, and with which insertion loss of the high-frequency signal is prevented from being increased.

An aspect of embodiments of the present invention is that a semiconductor package includes a base substrate on which a semiconductor element is disposed; a covering member which is provided to the base substrate, which covers the semiconductor elements, and which includes an opening at an end thereof at the side of the base substrate; and a connector substrate which is provided on the base substrate to close the opening, and which includes a first high-frequency signal line and a second high-frequency signal line. The first high-frequency signal line is in an area located in the covering member for a first surface. The second high-frequency signal line is on a second surface which is a surface on the opposite side of the first surface, and is electrically connected to the first high-frequency signal line. The base substrate is formed in a manner that the base substrate is located away from the second high-frequency signal line.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing a part of a conventional semiconductor package;

FIG. 2 is an exploded perspective view schematically showing a configuration of a semiconductor package of a first embodiment of the present invention;

FIG. 3 is a plan view showing a part of the semiconductor package shown in FIG. 2;

FIG. 4 is a cross-sectional view taken along the A-A line in FIG. 3;

FIG. 5 is an explanatory view showing various design values of the semiconductor package in a case of setting a characteristic impedance at 50Ω;

FIG. 6 is an exploded perspective view schematically showing a configuration of a semiconductor package of a second embodiment of the present invention; and

FIG. 7 is a cross-sectional view showing a part of the semiconductor package shown in FIG. 6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

A first embodiment of the present invention will be described with reference to FIGS. 2 to 5.

As shown in FIGS. 2 to 4, a semiconductor package 1A of the first embodiment of the present invention includes a base substrate 2; a semiconductor mounting part 3 which is provided on the base substrate 2, and which includes a plurality of semiconductor elements S; a covering member 5 which is provided to the base substrate 2, which covers the respective semiconductor elements S, and which includes an opening 4 at an end thereof at the side of the base substrate 2; and a connector substrate 6 which is provided on the base substrate 2 to close the opening 4, and which includes a first high-frequency signal line 7 a and a second high-frequency signal line 7 b. The first high-frequency signal line 7 a is in an area located in the covering member 5 for a first surface 6 a. The second high-frequency signal line 7 b is on a second surface 6 b (refer to FIG. 4) which is the surface on the opposite side of the first surface, and is electrically connected to the first high-frequency signal line 7 a.

The semiconductor mounting part 3 includes the semiconductor elements S; a mounting part 3 a which supports the semiconductor elements S; two matching condensers 3 b which are provided on the mounting part 3 a, and which are placed respectively on both sides of an array of the semiconductor elements S. These matching condensers 3 b are electrically connected to the respective semiconductor elements S by wire bonding or the like.

The covering member 5 includes a frame 5 a which is formed into a frame-like shape, and which is provided on the base substrate 2; and a lid member 5 b which is a lid body provided on the frame 5 a. The semiconductor mounting part 3 is housed in the covering member 5. Thereafter, the semiconductor mounting part 3 is hermetically sealed in the covering member 5. Two openings 4 are provided to the frame 5 a in a way that the two openings 4 face each other. These openings 4 are respectively situated on ends at the side of the base substrate 2.

The connector substrate 6 is a substrate which is formed into a plate-like shape, and which is formed of dielectrics having a certain permittivity. The connector substrate 6 functions as a member which closes the openings 4 of the frame 5 a. To the first surface 6 a of the connector substrate 6, the first high-frequency signal line 7 a is provided in a manner that the first high-frequency signal line 7 a is located inside the frame 5 a, and a third high-frequency signal line 7 c is provided in a manner that the third high-frequency signal line 7 c is located outside the frame 5 a. Furthermore, the second high-frequency signal line 7 b is provided to the back surface which is the second surface 6 b (refer to FIG. 4) of the connector substrate 6.

The first high-frequency signal line 7 a, the second high-frequency signal line 7 b, and the third high-frequency signal line 7 c are respectively transmission lines through which high-frequency signals pass. The first high-frequency signal line 7 a, the high-frequency signal line 7 b and the high-frequency signal line 7 c are connected to one another respectively through a plurality of through-hole wirings 8 formed on the connector substrate 6.

The first high-frequency signal line 7 a is extended from an internal end of the connector substrate 6, the internal end being towards the center inside the frame 5 a, in the direction toward an external end of the connector substrate 6 outside the frame 5 a, the internal end facing the external end. The first high-frequency signal line 7 a is provided up to a position in front of the frame 5 a so as not to contact therewith. The first high-frequency signal line 7 a is electrically connected to the matching condenser 3 b. The third high-frequency signal line 7 c is provided from a position in the vicinity of the frame 5 a to an external end of the connector substrate 6. The second high-frequency signal line 7 b is electrically connected to the first high-frequency signal line 7 a and to the third high-frequency signal line 7 c through the respective through-hole wirings. These first high-frequency signal line 7 a, the second high-frequency signal line 7 b, and the third high-frequency signal line 7 c are formed of, for example, a W thick film or a Cu thick film, Ni plating, Au plating, and the like. The through-hole wirings 8 are formed into blind through-holes for a hermetic seal.

To the third high-frequency signal line 7 c, a lead wire 9 is provided to draw out the third high-frequency signal line 7 c from the semiconductor package 1A. The lead wire 9 is electrically connected to the third high-frequency signal line 7 c.

The base substrate 2 is a substrate formed into a plate-like shape, and supports the back surface of the connector substrate 6, the back surface being the second surface 6 b. This base substrate 2 is formed of a material having high heat dissipation characteristics such as copper in a way that the base substrate 2 is located away from the second high-frequency signal line 7 b. That is, a concave part 2 a is provided to the base substrate 2. The concave part 2 a faces the second high-frequency signal line 7 b, and is located away from the second high-frequency signal line 7 b. Thus, in a case where the connector substrate 6 is provided on the base substrate 2, the base substrate 2 is prevented from contacting with the second high-frequency signal line 7 b.

The concave part 2 a is formed by removing a part of the base substrate 2, the part having a region larger than the second high-frequency signal line 7 b, the region including a region which faces the second high-frequency signal line 7 b. Because of the presence of the concave part 2 a, a space is provided between the second high-frequency signal line 7 b and the base substrate 2. This space is filled with air, and an air layer is formed therein.

As described above, in the first embodiment of the present invention, the second high-frequency signal line 7 b is provided to the second surface 6 b of the connector substrate 6, and the base substrate 2 is formed in a manner that the base substrate is located away from the second high-frequency signal line 7 b on the second surface 6 b. Thereby, the second high-frequency signal line 7 b, which passes under the frame 5 a, functions as a micro-strip line part. At this time, the air layer under the second high-frequency signal line 7 b is dielectrics (∈1>∈2). For this reason, in order to match impedance of the first high-frequency signal line 7 a and the second high-frequency signal line 7 b, and of the third high-frequency signal line 7 c and the second high-frequency signal line 7 b, it is necessary to set the width W2 of the second high-frequency signal line 7 b larger than the widths W1 respectively of the first high-frequency signal line 7 a and of the third high-frequency signal line 7 c. Accordingly, the allowable current of the second high-frequency signal line 7 b is increased, and melting of the second high-frequency signal line 7 b due to high power can be suppressed. Hence, insertion loss of a high-frequency signal can be prevented from being increased.

Moreover, since a part of the base substrate 2, the part facing the second high-frequency signal line 7 b is thin, it is made possible to suppress the occurrence of wraparound of a high-frequency signal at the time when the high-frequency signal passes the lead line 9. Accordingly, a high-frequency property can be enhanced. At this time, the base substrate 2 is made only partially thin, and is prevented from being made entirely thin. Hence, the mechanical strength of the base substrate 2 can be maintained.

The base substrate 2 includes the concave part 2 a which faces the second high-frequency signal line 7 b, and which is located away therefrom. Thereby, with a simple constitution, the second high-frequency signal line 7 b passing under the frame 5 a can be constituted as a micro-strip line part. Furthermore, the base substrate 2 can be easily formed in a manner that the base substrate 2 is located away from the second high-frequency signal line 7 b.

In this event, as shown in FIG. 3, the width of the first high-frequency signal line 7 a is indicated as W1, the width of the second high-frequency signal line 7 b as W2, and the width of the concave part 2 a as W3. As shown in FIG. 4, permittivity of the connector substrate 6 is set as ∈1, permittivity of air as ∈2, the thickness of the connector substrate 6 as t1, and the depth of the concave part 2 a, i.e. the thickness of the air layer, as t2. In this case, when the semiconductor package 1A is designed with characteristic impedance set at 50Ω, various kinds of design values are obtained as those of Example shown in FIG. 5. Incidentally, a conventional semiconductor package was used for Comparative Example.

As shown in FIG. 5, in Example, the width W2 of a high-frequency signal line (the second high-frequency signal line 7 b) was 0.644 mm. In Comparative Example, the width of a high-frequency signal line (a triconductor part 106 a: refer to FIG. 1) was 0.148 mm. In addition, in Example, the width of a ground conductor was the width W3 of the concave part 2 a, and was 3.0 mm. In Comparative Example, the width of a ground conductor was infinite (the width of the base substrate 102: refer to FIG. 1). Thus, with the semiconductor package 1A, a high-frequency signal line can be designed to have a width much larger than that of a strip line. Thereby, the allowable current of a connector part can be made large. In addition, the third high-frequency signal line 7 c can be designed to have a width in the range of not less than W1 to not greater than W2. Thereby, the fastening strength of the lead wire 9 can be increased. Moreover, the width of the ground conductor can be reduced by the thickness t2 of the air layer. Hence, a favorable high-frequency property can be obtained.

Second Embodiment

A second embodiment of the present invention is described with reference to FIGS. 6 and 7.

In the second embodiment, different parts from those of the first embodiment are described. In the following descriptions and the drawings, the identical reference numerals are used to designate the identical or similar components, the descriptions of which will be omitted.

As shown in FIGS. 6 and 7, to a base substrate 2 included in a semiconductor package 1B of the second embodiment of the present invention, a notch part 2 b is provided in place of the concave part 2 a in the first embodiment. The notch part 2 a is located away from a second high-frequency signal line 7 b. Thereby, in a case where a connector substrate 6 is provided on the base substrate 2, the base substrate 2 is prevented from contacting with the second high-frequency signal line 7 b.

The notch part 2 b is formed by notching a part of the base substrate 2, the part having a region larger than the second high-frequency signal line 7 b, the region including a region which faces the second high-frequency signal line 7 b. Because of the presence of the notch part 2 b, a portion of the base substrate 2 in a position, which faces the second high-frequency signal line 7 b, does not exist.

As described above, in the second embodiment of the present invention, a similar effect as that of the first embodiment can be obtained. Furthermore, by providing the notch part 2 b to the base substrate 2, a portion of the base substrate 2 in a position, which faces the second high-frequency signal line 7 b, does not exist. Thereby, the occurrence of wraparound of a high-frequency signal at the time when the high-frequency signal passes a lead wire 9 can be more reliably suppressed compared with the case of the first embodiment. In addition, the lead wire 9 can be directly connected to the second high-frequency signal line 7 b. In this case, the third high-frequency signal line 7 c is not needed.

Incidentally, since the base substrate 2 includes the notch part 2 b formed away from the second high-frequency signal line 7 b, with a simple constitution, the second high-frequency signal line 7 b passing under the frame 5 a can be constituted as a micro-strip line part. Furthermore, the base substrate 2 can be easily formed in a manner that the base substrate 2 is located away from the second high-frequency signal line 7 b.

Other Embodiments

It is to he understood that the present invention is not limited to the above-described embodiments, and various changes may be made therein without departing from the spirit of the present invention.

For example, in the above-described embodiments, various kinds of values have been described. However, the values are merely illustrative and not restrictive.

Moreover, in the above-described embodiments, respectively by way of the through-hole wirings 8, the second high-frequency signal line 7 b is electrically connected to the third high-frequency signal line 7 c which is on the first surface 6 a of the connector substrate 6, and the lead wire 9 is connected to the third high-frequency signal line 7 c. It is, however, not limited to the above. For example, the lead wire 9 may be connected to the second high-frequency signal line 7 b without providing the third high-frequency signal line 7 c. 

1. A semiconductor package comprising: a base substrate on which semiconductor elements are disposed; a covering member which is provided to the base substrate, which covers the semiconductor elements, and which includes an opening at an end thereof at the side of the base substrate; and a connector substrate which is provided on the base substrate in a manner that the connector substrate closes the opening, which includes a first high-frequency signal line in an area located inside the covering member for a first surface, and which includes a second high-frequency signal line on a second surface being a surface on the opposite side of the first surface, the second high-frequency signal line being electrically connected to the first high-frequency signal line; wherein the base substrate is formed in a manner that the base substrate is located away from the second high-frequency signal line.
 2. The semiconductor package according to claim 1, wherein the base substrate includes a concave part which faces the second high-frequency signal line, and which is located away from the second high-frequency signal line.
 3. The semiconductor package according to claim 1, wherein the base substrate includes a notch part located away from the second high-frequency signal line. 